The conventional device for focusing an objective lens in an optical system such as a night vision imaging system is shown in FIGS. 1 and 2. An objective lens 15, comprising as many as 5 or 6 individual lenses, is held inside a cylindrical objective cell or objective lens housing 14. A cylindrical LIF (light interference filter) 12 is bonded to a first segment 16 of the objective lens housing. A circumferential groove 18 around the outside surface of segment 16 receives a snapping feature (not shown in FIG. 1) of the LIF adaptor. A second segment 20 of the objective lens housing has an outside diameter that is smaller than the outside diameter of first segment 16. Second segment 20 is divided into two parts 23 and 26. Part 23 is adjacent part 22 of segment 16. Part 26 is adjacent circumferential groove 24 and includes the end of the objective cell. Circumferential groove 24 is formed around the outside surface of second segment 20 for receiving an O-ring 46.
A cylindrical first knob 28 is coupled to part of first segment 16 identified by reference 22. First knob 28 is a focus knob. Part 22 is bonded to the inside circumferential surface 30 of knob 28. Another inside segment 34 of the inside surface of knob 28 is threaded. A circumferential stop 32 separates the circumferential flat surface 30 from the circumferential threaded surface 34. A cylindrical second knob or stop adaptor 36 has a circumferential outside threaded surface 38 which may mate with the circumferential inside threaded surface 34 of knob 28.
After knob 28 is bonded to lens housing 14, stop adaptor 36 may be threaded onto knob 28. Stop adaptor 36 also has a circumferential outside smooth surface 39 which may be coupled to other parts of the night vision imaging system. When the stop adaptor is coupled to the remainder of the night vision imaging system, it does not rotate relative to the night vision system. That is, stop adaptor 36 is held stationary relative to the night vision system.
When the conventional device 10 is mounted into a night vision system, the user of the system may want to refocus the lenses inside lens housing 14 by moving the lenses in a translational direction along the optical axis of the lenses. The optical axis of the lenses is substantially parallel to the longitudinal axis of the lens housing 14. Since the stop adaptor 36 is held motionless relative to the night vision system, knob 28 may be rotated relative to stop adaptor 36 via the mating threads on the inner surface 34 of knob 28 with the threads on the outer surface 38 of the stop adaptor 36. Rotating the knob 28 will cause the knob to move in a translational direction with respect to stop adaptor 36. Because knob 28 is bonded to lens housing 14, the lens housing and its internal lenses will simultaneously move in a longitudinal translation direction along the optical axis of the lenses.
Knob 28 has a series of extensions 45 that extend outwardly from the outer surface of knob 28. The width of each extension 45 may be equal to be the width of knob 28. In an exemplary embodiment, there may be four extensions arranged at 90 degree intervals around the outer surface of knob 28. In an alternative embodiment, there may be more or fewer extensions 45. Each of the extensions 45 has a hole threaded into it. Threaded hole 44 extends completely through the entire width of extension 45. A threaded stop pin 42 may be threaded into any one of the threaded holes 44. The length of threaded stop pin 42 exceeds the width of extension 45. In fact, the length of stop pin 42 may be at least equal to the width of knob 28 plus the width of stop adaptor 36. The purpose of stop pin 42 is to prevent knob 28 from rotating more than one time relative to stop adaptor 36. This limitation of rotation function is accomplished because stop 40 prevents knob 28 from rotating any further when stop pin 42 bumps up against stop 40.
Because knob 28 is bonded to lens housing 14, rotation of knob 28 rotates lens housing 14 at the same time that it moves lens housing 14 in a translational direction. Because the conventional device causes the objective lens housing to rotate during focusing, the conventional device does not provide system compatibility with certain night vision imaging systems. Some systems require a rotationally stationary mounting. If these night vision systems are mounted to the conventional objective lens housing, the objective lens cannot be refocused without first removing the night vision system because the attached night vision system will not permit the lens housing to rotate.
To overcome the shortcomings of the conventional device, a new lens focusing device is provided.